This invention concerns a device to produce electronic circuits, particularly those comprising a base support consisting of very thin sheets of alumina and plastic materials, commonly known as xe2x80x9cgreen-tapexe2x80x9d.
The device according to the invention is able to process, in a completely automatic fashion, sheets of green-tape, already cut to measure according to the final destination of the circuit or electronic plate to be produced, to perform three operations: to deposit the conductor material by means of serigraphy, the drying operation in the oven, and also the cooling operation. In this way the product which emerges from the device is ready for the subsequent working steps, that is to say, the assembly of several supports to achieve multi-layer circuits, and/or the assembly of the electronic components.
One of the techniques well-known in the production of electronic circuits is to use as a base support one or more sheets of insulating material, consisting of alumina or synthetic materials, according to the green-tape technology.
The green-tape supports are normally arranged on rectilinear guides along which they are fed in sequence, by means of a feed mechanism, from a loading station to a printing station where, by means of serigraphy, the conductor material is deposited thereon, in the form of a conductor paste, according to a pre-defined mask. Subsequently, each support is introduced into a drying oven, where it is kept at a temperature of at least 120xc2x0 C. for the time needed to make the conductor paste set, which time at present is at least ten minutes.
After the drying operation in the oven, the supports are cooled in a suitable cooling chamber and then discharged from the device.
Conventional devices have the disadvantage of being very bulky, with a linear development of several tens of metres. This depends on the fact that all the steps described above occur in serial sequence, and that in the drying oven alone the line develops for more than 10 metres.
In fact, if we consider that the time needed to perform a single serigraphy operation is about 10 seconds, and that the length of each support is several tens of centimetres, we can see that the average speed of feed of the supports along the rectilinear guides is about 1-1.5 m/min.
Consequently, as we have seen, each support must stay inside the drying oven for at least 10 minutes, and the development of the line inside the drying oven may be even more than 10 metres.
The state of the art includes devices with a linear-type drying oven, that is, more than 10 metres long, with consequent disadvantages from the point of view of bulk, and also devices where the drying oven develops partly upwards. In this latter type, there is a conveyor belt system inside arranged in a coil, on which brackets are attached; on each bracket one or more supports to be dried are rested. This second solution has the disadvantage that it is both complex and expensive, and requires that the supports which are to be dried are handled, in order to arrange them on the brackets of the oven and to remove them therefrom.
The present Applicant has devised and embodied the device to produce electronic circuits according to the invention to overcome these shortcomings.
The device to produce electronic circuits according to the invention is set forth and characterized in the main claim, while the dependent claims describe other innovative characteristics of the invention.
One purpose of the invention is to achieve a device to produce electronic circuits which is simple and not cumbersome, and which, at the same time ensures high quality.
Another purpose of the invention is to achieve a device to produce electronic circuits wherein all the operations to deposit the conductor paste, and the drying and cooling steps are carried out automatically and very quickly, so as to obtain a high hourly productivity.
In accordance with this purpose, the device according to the invention, to produce electronic circuits of the type comprising at least a base support on which electrically conductive material is deposited, able to embody the conductor tracks, comprises at least a printing station able to deposit the electrically conductive material onto the base support, a drying oven and feed means to feed each base support from the printing station to the drying oven. According to one characteristic of the invention, stacking means are provided to stack the base supports one on top of the other, after they have been processed in the printing station, so that they can be introduced in vertical piles into the drying oven, and spacer means are provided to keep the base supports separate from each other when stacked.
According to one characteristic of the invention, the drying oven comprises a drying chamber inside which at least one pile of base supports is able to be inserted, and means to circulate a current of hot air in a direction transversal to the pile, so that a plurality of base supports, with the relative electronic circuits deposited thereon, can be dried simultaneously.
According to another characteristic of the invention, the drying oven is of the modular type, so that two or more modules can be placed adjacent to each other in a longitudinal direction, that is, in the direction of feed of the base supports.
According to another characteristic of the invention, downstream of the drying oven there is a cooling unit through which each pile of base supports is fed in such a manner that it can be lapped by a current of cold air, in a direction transversal to the pile, so that a plurality of base supports, with the relative electronic circuits deposited thereon, can be cooled simultaneously.
According to another characteristic of the invention, the feed means for the base supports comprise a first rectilinear guide able to guide the base supports, one in front of the other and separated by a determined pitch, from the printing station towards the stacking means, and a second rectilinear guide able to guide the piles of base supports, one in front of the other and separated by the same pitch, from the stacking means to a collection station through the drying oven.
According to another characteristic of the invention, the printing station is displaced laterally with respect to the rectilinear guide of the base supports, and transverse feed means are provided to move the base supports transversely, one at a time, from the rectilinear guide to the printing station and vice versa.
According to another characteristic of the invention, the device is able to manage advantageously other base supports of a flexible type, for example of the green-tape type. In order to do this, the spacer means comprise a rigid supporting plate for each base support, on the upper surface of which a base support is able to be rested.